Driven by the sheer popularity of mobile devices, data-intensive applications, and emerging paradigms such as the Internet of Things (IOT), traffic volume is predicted grow exponentially. To keep pace with the growing traffic demands, wireless network are expected become more dense and heterogeneous in the future.
With such massive access point (AP) deployments, the backhaul links connecting the APs to the network backbone, or “cloud,” are also expected to become denser. However, given the excessive costs associated for a highly-reliable wired backhaul, future backhaul links will most likely be wireless and thus inherently unreliable. Moreover, this network densification will also make backhaul deployment more challenging due to topology and access issues. This suggests that the future backhaul infrastructure would mostly comprise non-line-of-sight (non-LOS) links. This marks a departure from conventional wireless networks, which have traditionally been assumed to have highly reliable, e.g., by optical fiber or LOS wireless backhaul links.
For the above, see generally Andrews et al., “What will 5G be?” IEEE J. Sel. Areas in Commun., vol. 32, pp. 1065-1082, June 2014, Andrews, “Seven ways that HetNets are a cellular paradigm shift,” IEEE Commun. Mag., vol. 51, pp. 136-144, March 2013, Tipmongkolsilp et al., “The evolution of cellular backhaul technologies: Current issues and future trends,” IEEE Commun. Surveys Tutorials, vol. 13, pp. 97-113, 2011, and Coldrey et al., “Small-cell wireless backhauling: A non-line-of-sight approach for point-to-point microwave links,” Proc. IEEE Veh. Tech. Conf., Canada, September 2012.
This paradigm shift in wireless network architecture has spurred significant interest in the design and analysis of wireless networks with unreliable backhaul links. The impact of finite capacity backhaul on network performance and optimal compression schemes is described by Simeone et al., “Robust communication via decentralized processing with unreliable backhaul links,” IEEE Trans. Inf. Theory, vol. 57, pp. 4187-4201, July 2011, and references therein. There, the assignments are fixed assignment, and the unreliable nature of the backhaul link is dealt with using compression of the message.
Another line of work considers cooperative wireless network with heterogeneous backhaul, see Pantisano et al., “On the impact of heterogeneous backhauls on coordinated multipoint transmission in femtocell networks,” Proc. IEEE Int. Conf. Commun., June 2012. There, a game-theoretic approach is used to study the impact of a heterogeneous backhaul on the downlink performance of a cooperative femtocell network.
In related work, the downlink of a coordinated multi-point network is considered to study the impact of unreliable backhaul on network performance, see Z. Mayer, J. Li, A. Papadogiannis, and T. Svensson, “On the impact of backhaul channel reliability on cooperative wireless networks,” in Proc. IEEE Int. Conf. Commun., Budapest, Hungary, June 2013. It was shown that unreliable backhaul could severely limit the performance gains promised by cooperation.
U.S. Pat. No. 6,748,212 describes a method to monitor the effect of adjacent and co-channel interference on a single backhaul link.
U.S. Publication describes a method for assigning a backhaul site to an access point via a beam steering approach where the AP has multiple antennas. There, a selection among multiple possible backhaul sites, based on the loading of each particular backhaul site, is conducted.
WO 2014093050 Patent describes a method for optimizing backhaul transport based on user data priority. When a highly reliable backhaul link becomes congested some of the low priority data can be switched onto a backhaul link with lower priority.
As described above, in modern wireless networks, it is not uncommon to encounter cooperative networks where a group of multiple wireless nodes (or APs) transmit a message to an end user (receiver or client) using the same time-frequency resources. A control unit (CU) is connected to each AP via unreliable backhaul links. The backhaul links are independent and can have different reliabilities. The CU needs to schedule the backhaul resources to communicate with each AP in order to maximize the overall communication reliability from the CU to the end user.